Abstract: An optical information transmission system capable of achieving an information transmission at a signal to noise ratio greater than that which is achievable using classical optical transmission techniques if disclosed. The higher signal to noise ratio is achieved by employing a non-classical, i.e. quantum mechanical, optical transmission technique. To achieve non-classical transmission effects, a non-degenerate optical parametric amplifier is employed to generate a pair of signal beams having highly correlated quantum noise. Information is then encoded within each of the signal beams at a signal level far below the level of the quantum noise. Accordingly, information encoded on the beams is substantially obscured by the quantum noise, thereby effectively preventing unwanted eavesdropping of the transmitted information. After transmission, the pair of separate signal beams are detected and combined by a receiver.

Abstract: Squeezed states of light having significant degrees of squeezing are achieved with modest values of atomic density and intracavity electromagnetic (EM) field by a device and method for coupling the EM field within the optical cavity. An oscillatory exchange of excitation then occurs between the atomic polarization and the EM field within the cavity.

Abstract: Quantum nondemolition measurements are made by back-action evasion obtained by a combination of a parametric oscillation and a conversion of polarizations. A polarization converter (14, 16, 17), such as a Faraday rotator, converts at substantially a single frequency between at least a portion of a signal polarization state and a detector polarization state. A parametric amplifier (11) having a gain G is coupled to the polarization converter (14, 16, 17).

Abstract: Resonant optoacoustic cells are used in measurements of the concentration and composition of a gas or aerosol. Such apparatus is improved by providing a small absorption cell acoustically coupled to a resonant acoustic cavity so that the time delay associated with the flow of a gas or aerosol through the absorption cell is greatly reduced.